maintain high activity towards adenosinereceptors; in fact, pteridine derivatives did not show themselves to be good adenosinereceptorligands. On the contrary, N6‐cycloalkyl‐ or N6‐alkyl‐2‐phenyladenines showed a very high affinity and selectivity for A1 adenosinereceptors. We demonstrate also that the 9‐benzyl substituent is crucial for conferring high affinity for A3 receptors to molecules having a